Conventionally, a motor for rotating a disk is provided at its top portion with a chucking device that removably holds the disk. The chucking device includes a centering case which brings the center of the disk into alignment with the rotational axis of the motor (hereinafter simply referred to as “centering”) and a turntable having a disk support surface for supporting the disk. In general, the chucking device is fastened to a rotating shaft of the motor (see, e.g., Japanese Patent Laid-open Publication No. H5-334779 that discloses a conventional motor provided with a chucking device).
A structure of the conventional motor la provided with a chucking device as disclosed in Japanese Patent Laid-open Publication No. H5-334779 will be described with reference to FIG. 12, which is an axially-cut schematic section view of the conventional motor.
Referring to FIG. 12, the motor la includes a rotating member that rotates about a specified center axis J1 and a fixed member that rotatably supports the rotating member. A chucking device 2a is attached to the axial top portion of the rotating member. The rotating member has a rotating shaft 1a1 arranged coaxially with the center axis J1. The chucking device 2a includes a resin-made turntable part 2a1 fixedly secured to the shaft 1a1, the turntable part 2a1 having a disk support surface 2a11 for supporting a disk (not shown), and a centering case 2a2 which brings the center of the disk into alignment with the center axis J1.
In keeping with a recent demand for a low-profile disk driving apparatus, there is an increasing need to reduce the thickness of a motor. In a motor provided with a chucking device, the chucking device is made thin in an effort to accomplish thickness reduction of the motor without sacrificing the characteristics thereof.
During the course of fitting a motor to a disk driving apparatus, however, there is a possibility that a worker who engages in the task of assembling the disk driving apparatus may inadvertently press a disk support surface of a chucking device. The turntable part 2a1 may possibly be deformed at this time, because the axial length of a coupling portion between the shaft 1a1 and the turntable part 2a1 cannot be sufficiently obtained due to reduction in the thickness of the chucking device and because the turntable part 2a1 is made of a resin material. As a result, a disk may be deflected during its rotation and an error may possibly be generated when recording information on or reproducing information from the disk. Another problem resides in that vibration may be generated due to deflection of the disk during its rotation.